Flame hardening control



1.1; J. 'CROWE 2,293,281 FLAME-HARDENING CONTROL filed 1:00.. '10. 1940 ATToR Ey.

' ations.

Patented Aug. 18, 1942 UNITED STATES, PATENT OFFICE FLAME CONTROL I I I John J. Crowe, Westiield, N. 3., assignor to Air Reduction Company, Incorporated, New York, N. Y., a corporation of New York Application December 10, 1940, Serial No. 369,395

is not sufliciently perfect to obtain true uniform- Claims. This invention relates to' the hardening or work-pieces that are made of metal which can be hardened by cooling quickly from above a critical temperature, and that are hardened by moving a system of heating flames progressively across the metal-piece followed by quenching jets that are directed against the hot metal a short,

distance behind the heating flames.

In the flame hardening of heavy sections, there are large heat losses by conduction from metal just below the surface into the mass of underlying metal. In order to obtain flame hardening to a given depth, it is necessary that the metal be heated above its critical temperaturefor that depth at the time of the quench. A heating torch that generates enough heat to produce the desired results when operating over a heavy section at ,a given speed, and that moves over much thinner sections at the same speed, will heat the thinner section above its critical temperature to a greater depth and cause resulting variations in the depth of hardening at different sections ofthe work-piece.

improved method and apparatus for controlling the depthof hardening in flame hardening oper- When hardening a work-piece with this invention the distance between the heating flames and quenching jets is changed with variations in the thickness of the work to bring the quench nearer to the flames at regions where the work-piece-is thin, and further from the re- I gion of heating as the mass of metal below the surface increases.

There is a substantial heat loss by conduction through the metal from the region where the heating flames are applied to the region where the quenching jets strike the work-piece. The

shorter the distance between these regions of heating and cooling, the greater the heat transfer between them, and the greater this heat loss, the shallower will be the layer of metal that is heated above its critical temperature, if other conditions remain the same.

By varying the spacing of the quenching jets from the heating flames so as to make the conduction losses to the quenching region vary in inverse proportion to the changes in conduction losses to theunderlying metal at sections of different thickness, the depth of metal heated above its critical temperature can be kept substantially constant and the depth of hardness produced kept substantially uniform along the entire length of the work-piece. Even though the regulation ity in the depth of hardening, any variation in the heat loss from the region of heating to the quenching jets that is inverse to a change in the mass of metal below the torch is beneficial in obtaining more uniform depth of hardening.

In accordance with one feature of the invention the angle at which the quenching Jets are directed against the work is changed to cause the jets to slope toward or away from the region at which the heating jets strike the work. This makes possible a change in the spacing or proximity of the quenching jets and the heating flame with much simpler apparatus than if the quenching jets are always kept in parallel positions, but the invention is not limited to such changes in the angul-arity of the quenching jets as an ex-- pedient for changing their spacing from the heating flames. I i

Another object of the invention is to provide automatic means for changingthe proximity of sults desired, whether uniform or variable hardness.

Other objects, features, and advantages of the invention will appear or be pointed out as the specification proceeds.

In the accompanying drawing, forming a part hereof:

Fig. 1 is a side elevation, largely diagrammatic,

showing a work-piece and apparatus for flame hardening the work-piece in accordance with this invention.

.Fig. 2 is an enlarged detail view of a portion 'of the apparatus shown in Fig. 2.

Fig. 3 is a top plan view of the structure shown in Fig. 2.

A self-propelled torch carriage l0 runs on a track I I, being propelled by a motor l2, the speed A bracket I5 is connected to the carriage III by a double clamp l6 which grips a post 11 extending upward from the carriage Ill. The clamp 16 can be adjusted up and down on the post I! for workpieces of different height.

A heating torch I9 is secured tothe forward end of the bracket l5 and is supplied with a mixture of oxygen and fuel gas through a conduit 20 in a manner well understood in the art. The oxygen and fuel gas,, preferably acetylene, are discharged through orifices in the face of the torch and burn in heating flames 2| that are moved progressively across a work-piece 22 at such a speed that the heating flames raise the metal on the surface, and immediately below the surface, to a temperature well above the critical greater at some regions than at others, and the conduction losses to the metal below the surface are consequently uneven at the different regions. A quenching head24 is supplied with cooling medium, preferably water, by a tube 25, and the cooling medium is discharged through orifices in the face of the quenching head in the form of quenching jets 26. The head 24 is supported from the bracket l5 by pivots comprising screws 21 that thread through bifurcated ends ofthe bracket and into bearing sockets in the opposite ends of the quenching head. The tube 25 is flexible so as not to interfere with the angular movement of the'quenching head 24 about the pivot bearings at the ends of the screws 21.

A cam follower 29 contacts with a cam 30 that is detachably connected with the track II by bolts 3|. The cam 30 is held at a given distance from the track II by spacers 32 (Fig. 3). follower 29 is connected to the back of the quenching head 24, and the cam-follower is heavy enough to rock the quenching head 24 counterclockwise whenever there is a reduction in the elevation of the cam. Rises in the cam face displace the follower 29 and rock the quenching head 24 clockwise, the extreme positions on opposite sides-of the vertical being indicated by dotted lines in Fig. 2. The angular projection of the quenching jets against the work-piece 22 is also indicated in dotted lines.

It will be noted that with the quenching head rocked into the right-hand dotted-line position, the distance from the heating flames to the line on which the quenching jets strike the work is cut in half as compared with the full-line position shown in the drawing. 1

. Such a reduction in the distance between the metal under the flames and the region where the quenching jets. strike the work substantially increases the rearward -conduction losses from the region of heating and influences the depth to which the metal is heated above its critical temperature.

The cam 30 is designed for the particular work-piece 22. When other work-pieces having different sizes and changes in thickness are to be hardened, a different cam is used.

At the beginning of a hardening operation the heating torch I9 is held stationary for a short period or moved very slowly toward the right across the surface of the work-piece 22 While the quenching head is-not in use and before the cam follower 29 reaches the left-hand end of the cam 30.

When the heating flames are first applied to the work-piece there are substantial conduction losses downward, and forward, into the cold metal ahead of the torch. Soon after the carriage I0 is started under its own power, and the torch l9 begins its progressive movement across the work-piece 22, the cam follower 29 reaches the cam 30 and the quenching jets are started by supplying fluid to the tube 25. The left-hand end of the cam is low so that the quenching head 24 slopes .in a direction to project its jets The cam downward toward the region of heating. This- .position of the quenching head 24, corresponding to the right-hand dotted-line position of the quenching head 24 shown in Fig. 2, causes the quenching jets to withdraw large quantities of heat from the metal under the torch and compensates for the small conduction losses down-' wardat the section where the work-piece is relatively thin.

As the torch reaches the surface above the web of the work-piece where downward conduction losses become substantial, the cam follower 29 encounters a rise in the cam 30 and is displaced clockwise so that the quenching head 24 rocks back into a rearwardly inclined position, as indicated by the left-hand dotted-line position shown in Fig. 2. The quenching jets are thus moved further from the region where the flame jets 2| strike the work-piece and'the conduction losses to the quenching region thereby reduced to counteract the increase in the heat loss downward into the web.

As the torch I9 moves over the end of the workpiece 22 beyond the web, the cam follower 29 passes down a drop in the cam 30 and moves the quenching head counterclockwise so that the jets 26 strike the work-piece closer to the heating flames 2| and increase rearward conduction losses downward where the section'is of only intermediate thickness.

Toward the end of the work-piece where there is no cold metal ahead of the heating torch, the quenching jets are brought as close to the flames '2I as possible to compensate for the reduced conduction of heat into metal ahead of the torch.

If non-uniform depth of'hardening is desired, a cam of different design is used, the contour of the cam being such that the quenching jets are shifted away from the flames at regions where hardening to a greater depth is desired, and the other way for a shallower section of hardened metal.

The envelope gases from the heating flames spread over the hot metal and protect it from the atmosphere prior to quenching. The envelope gases also prevent the quenching water from splashing in under the heating torch when the quenching jets are directed at an angle toward the flames.

One'embodiment of the invention has been described, but it will be understood that many others are possible without departing from the invention as defined in the claims.

'1 claim:

1. The method of producing a uniformly hardened face on a work-piece of variable thickness below said face and made of material which can be hardened by cooling quickly from above a critical temperature, which .method comprises heating above said critical temperature the face to be hardened by means of heating flames ap-' plied progressively to the face of the work-piece in a manner that supplies substantially equal heat input to the regions of different thickness, directing jets of quenching fluid against the heated face close behind the progressively-applied heating flames, and changing the proximity of the quenching jets and'heating flames so that the quenching jets strike the face of the workpiece further from the heating flames at regionswhere greater thickness of metal under the flames causes larger heat loss by conduction.

2. The method of flame hardening a part that is made of material which can be hardened by cooling quickly from above a critical tempera- 'temperature, followed by a system of quenching jets, and compensating for variations in the heat piece that is made of material that can be hardened by moving heating flames progressively across the face to be hardened to raise said face above its critical temperature, followed by quenching jets close behind the heating jets, the improvement which comprises shifting the quenching jets closer to or further from the heating flames in such relation to variations in the section of the work-piece that the jets heat respect to the heating torch in a direction to shift the quenching jets closer to or further from the heating torch during the progress of the torch and quenching head across a work-piece, quenchcontrol means movable with the carriage, and a connection through which said quench-control means moves the quenching head on said suppor 7. Flame hardening apparatus comprising a supporting means that has relative movement with respect to a work-piece, connections for atthe metal above its critical temperature for substantially the same depth at different regions regardless of said variations in the section and consequent differences in heat losses from the surface;

4. Themethod of flame hardening a workby cooling quickly from above a critical temperature, which method comprises heating the workpiece above its critical temperature progressively along the length'of. said surface by moving a constant number of heating flames at substantially uniform speed, following said heating flames with quenching jets directed against the heated workpiece close behind the heating flames, and controlling the hardening at diflerent regions by changing the inclination of the quenching jets with respect to the work-piece so that durin their progress across the work-piece they strike said work-piece at different distances from the heating flames.

5. In the flame hardening of a that is made of metal that can be hardened by cooling quickly from above a critical temperature and that is heated by flame jets which are moved progressively across the surface of the piece, but

which would leave the metal a short distance behind them heated above its critical temperature for different depths at different regions across the work-piece because of variations in conduction losses resulting from diflerences in the mass of metal below the heated-surface, the improvement which comprises progressively applying quenching jets to the work-piece at some distance be"- hind the heating names and varying the distance between the heating flames and quenching jets during the hardening operation by moving the I work-piece taching a heating torch and a quenching head to the supporting means, said connections including a bearing on which the quenching head is freely movable to change the distance between the heating flames of the torch and the jets delivered by the quenching head during a flame hardening operation, and a device connected with the quenching head and operable in response to the relative movement of the supporting means and the work-piece for moving the quenching head on said bearing.

8. Apparatus for flame hardening a work-piece that varies in thickness along its length, said apparatus comprising a carriage movable along a given course to traverse a heating torch and a quenching head across the work-piece, bearing means for supporting the quenching head for movement with respect to the heating torch, a cam follower for moving the quenching head on said bearing means, and a-cam extending along the course of the carriage and having a displacement contour corresponding to changes in the that varies in thickness along its length, said apparatus comprising a carriage movable along a given course to traverse a heating torch and a quenching head across the work-piece, bearing means for supportingthe quenching head for movement with respect to the heating torch, a cam extending along thecourse of the carriage and located in a definite relation to the workpiece, and means for moving the quenching head on said bearing means including a cam follower in position to travel along the cam as the carriage moves along its course, the cam having changes in elevation at the successive portions ofthe cam follower that correspond with the arrival of the quenching headat regions where there is a change in thickness of the work-piece.

10. Apparatus'for flame hardening including in combination a carriage support comprising a "track, a self-propelled torch carriage with wheels running on the track and a governor-controlled motor for moving the carriage at uniform speed, a support for a work-piece at one side of the track, a cam detachably connected to one of the supports, a heating torch, a bracket connecting the heating torch with the carriage, a quenching head, alined pivots connecting the quenching head with the bracket a short distance behind the heating torch and angularly movable on said pivots about an axis transverse of the direction of movement of the bracket as the carriage moves along the track, and a cam follower connected to the quenching headfor rocking said head on the pivots to cause the quenching head to direct its quenching jets angularly toward or away from the heating torch in accordance with changes in elevation on the contour of the cam.

' JOHN J. CROWE. 

